Sear release mechanism



y 1946. H. MOCLURE, JR 2,404,881

SEAR RELEASE MECHANISM Filed Jan. 26, 1944 .Wiijii MA m l a dufwwjxg Patented July 30, 1946 SEAR RELEASE MECHANISM Laurence H. McClure. Jn,

assignor to Colts Patent Fire Arms Manufacturing Company, Hartford, Conn, a. corporation of Connecticut West Hartford, Conn.,

Application January 26, 1944, Serial No. 519,702

9 Claims.

The present invention broadly relates to the combination of an automatic firearm having a breech casing provided On opposite sides with means adapted to support a trigger motor on one side or the other of the breech casing, a breech bolt reciprocable within the breech casing, a firing pin reciprocable within said breech bolt, a scar slidably mounted adjacent one end of the breech bolt, a scar slide guideway adjacent and extending transversely to said scar, and a sear slide assembly comprising a pair of members respectively mounted within said sear slide guideway, each of said members embodying a cam notch adapted to normally coincide with each other and independently cooperate with one of a plurality of cam surfaces on the sear to actuate the same and release said firing pin which is adapted to be held in cocked position by the sear. Specifically, the essence of the present invention comprises the sear slide assembly which is adapted to be mounted in a conventional sear slide guideway of existing breech bolts for automatic firearms, whereby no alteration of any parts of said firearms or standard trigger motors is required in order to utilize said sear slide assembly in the foregoing combination of parts in an automatic firearm.

Heretoiore, it has been customary to utilize a single sear slide adapted to be slidably mounted in a conventional sear slide guideway in a breech bolt, said sear slide extending inward from substantially one end of said guideway to and slightl past a cam faced member projecting from one s de of the sear into the sear slide guideway.

Said sear slide was provided with a cam surface :1

extending inward from one edge of the slide, said s rface being adapted to coact with one of said cam surfaces on the sear. When a trigger motor was mounted on the side of the breech casing adjacent the end of the guideway in which the outer end of the sear slide was disposed, said triggcr motor could be energized to move said sear slide into camming engagement with the scar and release the firing pin held in cocked position by the sear.

Automatic firearms of the type to which the present invention pertains are very commonly used in airplanes as well as on many different ypes of vehicle or stationary ground type mounts. Said firearms are frequently mounted in closely juxtaposed pairs, whereby it is necessary to mount a trigger motor on one side of one firearm and on the opposite side of the adjacent firearm. Under certain conditions, it is necessary or desirable to mount the trigger motor on one side or the other of the breech casing due to the surroundings of the firearm. In order that the use of the firearms may be rendered more flexibly adaptable to various mounting conditions, they are constructed so that the trigger motors may be mounted on either side of the breech casing. For the trigger motor to coact with the sear slide in the breech bolt, it has heretofore been necessary that the outer end of the sear slide be disposed in the end of the sear slide guidewa adjacent the side of the breech casing on which the trigger motor was mounted. If the trigger motor were changed from one side of the breech casing to the other, it was necessary to partially disasscmble the firearm to the extent of removing the back plate and render accessible the rear end of the breech bolt, reverse the sear slide Within the sear slide guideway and then reassemble the firearm.

Frequently firearms of the type referred to are mounted in inaccessible positions in airplanes or on mounts of various kinds used elsewhere, the firing of the firearms 50 mounted being controlled from a position remote from the firearms. Regarding remotely mounted firearms in airplanes particularly, when an airplane is in flight, it is generally impossible for a gunner to have access to the firearm for servicing or even for loading the firearm. When the firearm mounted in a remote position in an airplane such as referred to is serviced While grounded, should the trigger motor for any reason be changed from one side of the breech casing to the other without also reversing the sear slide in its guideway, said omission to reverse the sear slide will render that particular firearm useless when the airplane is in flight since the gunner, as stated, can usually not reach the gun for purposes of reversing the sear slide. Thus. a completely loaded firearm, under these circumstances, would be of no use until the airplane was subsequently grounded to permit reversing the sear slide in its guideway.

The present invention has been conceived to obviate the possibility of the occurrence of the foregoing undesirable circumstances. Thus, one object of the invention is to provide a scar slide assembly comprising interfitting component members respectively operable from either end of the sear slide guidcway by a trigger motor when mounted on either side of the breech casing, whereby the trigger motor may be changed from one side to the other of the breech casing and no servicing of the firearm of any kind, such as reversing the sear slide in its guideway, will be required.

Another object of the invention is to construct the component members of the sear slide assembly so that the overall dimensions of the assembly will permit the substitution of the assembly for the conventional single sear slide referred to in the foregoing.

It is a still further object of the invention to so construct the component parts of the sear slide assembly that said assembly may be slidably mounted in its guideway without requiring the disassembly of any of the component parts of the breech bolt; it merely being necessary to move the rearward end of the breech bolt to a position slightl beyond the rearward end of the breech casing so as to expose the opposite ends of the sear slide guideway.

Still another object of the invention is to provide a cam surface on each component part of the assembly so that said cam surfaces will be adapted to independently coact with the conventional earn surfaces on the sear, whereby the construction of the standard sear will not have to be modified in any way in order to utilize said sear slide assembly.

The details of the foregoing objects, as well as other objects and the details of the invention, appear in the following specification and are illustrated in the accompanying drawing.

The accompanying drawing shows the embodiment of the invention which is deemed preferable, but it will be understood that the drawing is intended for illustrative purposes only and is not to be construed as defining or limiting the scope of the invention, the claims forming a part of this specification being relied upon for that purpose.

In the drawin Fig. 1 is a vertically sectioned fragmentary side elevation of the rearward end of a, breech bolt including the sear slide assembly comprising the present invention.

Fig. 2 is a fragmentary rear end view of an automatic firearm embodying the present inventlon, part of the firearm being diagrammatically illustrated in dot and dash of the firearm being transversely and vertically sectioned to better illustrate the details of the present invention. In this view, a trigger motor is shown in its alternate positions on opposite sides of the breech casing.

Fig. 3 is an exploded perspective detail view of the sear slide assembly comprising the essence of the present invention.

Fig. 4 is a perspective view of a single con ventional sear slide.

The type of automatic firearm to which the present invention preferably, but not restrictively, applies is basically illustrated in U. S. Patent No. 1,628,226 to Browning. In said patent, a vertically movable sear is actuated by a trigger lever and no sear slide is illustrated. However, a firearm utilizing a vertically slidable sear and a horizontally slidable sear slide is shown, for example, in U. S. Patent No. 1,618,280. The sear slide in the latter patent is reversible in order to permit the mounting of a trigger motor on one side or the other of the breech casing.

Horizontally slidable scars and vertically slidable sear slides are illustrated in U. S. Patents Nos. 1,803,349 and 1,803,350, respectively, issued to Pfeiffer and Tansley. In the latter two patents, the sear slides are reversible in order to render the sears releasable by a trigger motor when said motor is mounted on either side of the breech casing.

lines and another part ,pivotally movable firing pin. Further .sear is unnecessary The sear slide conventionally used at present on firearms of the type illustrated is shown in Fig. 4, said slide being of one piece construction and reversing of said slide in its guideway is required when a trigger motor is changed from being mounted on one side of the breech casing to being mounted on the other side of the breech casing.

Referring to the drawing, the automatic firearm Ill comprises a breech casing ll having a pair of spaced side plates 12 and 14 which are respectively provided with means comprising slots 16 and IB adapted to accommodate and support a trigger motor 20 when mounted on either plate I2 or M. Trigger motor 20 is of a conventional type and includes a reciprocable plunger 22 adapted to extend into the slots IE or l8 of the side plates. When the trigger motor is energized, either electrically or mechanically, plunger 22 is caused to move through the slots 16 or l8 and into the interior of the breech casing H.

Longitudinally reciprocable within the breech casing II is a breech bolt 24 which slidably supports a reciprocable firing pin 26 which is biased from cocked to firing position by a spring 28. The rearward end of the firing pin is provided with a dog or detent 36. A cocking lever 32 is about a transverse axis 34 and engages the rearward end of the firing pin 26 to move the same rearward to cocked position. Cooking lever 32 is actuated by a mechanism in the breech casing, details of which are fully described in said Patent No. 1,628,226.

A pair of opposed vertical guideways 36 are formed in the rearward end of the breech bolt to accommodate opposed flanges 38 respectively formed on opposite sides of a vertically movable sear which is normally biased upward by a spring 42. The inner side of the sear 4B is provided with a protruding catch 44 adapted to engage the detent 3B of the firing pin to hold the latter in cocked position after the same has been moved to said position by the cooking lever 32.

The rearward face of the sear 46 is provided with a rearward extending projection 46 which is provided on its upper portion with a pair of opposed cam faces 43 and 50.

The rearward end of the breech bolt is also provided with a horizontal guideway 52 comprising opposed channels, the bottom channel intersecting the projection 46.

The sear 40 normally reciprocates vertically in a path sufllciently long to permit the catch 44 to disengage the detent 30 in order to release the downward movement of the but a slight amount of further downward movement is possible to insure releasing of the detent 39 under all circumstances. Downward movement of the sear 40 is limited by spring 42 becoming completely compressed.

Heretofore, in conventional breech bolts, 5:, sear slide 54 was slidably mounted in guideway 52 and was provided on each of its top and bottom edges with a guide rib 56 respectively accommodated in the opposed channels of said guldeway. A cam notch 58 extended upward from the bottom edge of the slide and said bottom edge was cut away between the cam notch 58 and the inclined inner end 80 to provide a clearance space for purposes to be described. The inclined end 69 engaged one of the cam faces 48 or of the sear, when the slide 54 was introduced into the guideway from one end or the other thereof, and cammed the sear downward, the clearance space at the lower edge of the slide being adapted to pass or clear the projection 46 of the sear in order that the cam faces 48 and 50 thereof might be disposed against the walls of the notch 58 of the slide. The inner end of the slide terminated a substantial distance from the end of the guideway opposite that from which the slide was introduced. Movement of the sear downward was sufficiently limited that the sear slide could not be mounted in the guideway in the manner described unless said clearance space was provided on the sear slide.

If a trigger motor 20 were mounted, for example, on the left side plate of the breech casing, the sear slide 54 was mounted with its larger or outer end adjacent the plunger 22 of the trig er motor whereby, when the plunger was actuated, the sear slide was moved inward and the longer wall of the notch 58 engaged the cam face 48 to depress the sear and release the firing pin from cocked position. When the trigger motor plunger disengaged the sear slide, spring 42 biased the sear upward and moved the sear slide outward to its normal starting position.

However, when a trigger motor is changed from the left side of the breech casing to the right side thereof, it is necessary, when using a conventional sear slide 54, to disassemble the firearm sufflciently to expose the rearward end of the breech bolt the necessary amount to permit access to the guideway 52 in order that the sear slide 54 may be removed from the left hand end of the guideway and reinserted in the right hand end in order that the outer end of the slide may be in proper position to be engaged by the plunger of the trigger motor when mounted on the right hand side of the breech casing.

As stated in the foregoing, if a firearm of the type described is mounted in an inaccessible location, for example, in an airplane or elsewhere and the firing of the firearm is remotely controlled, the firearm will be useless following a changing of the trigger motor from one side of the breech casing to the other unless the sear slide has also been reversed within its guideway.

To overcome the necessity of having to reverse the sear slide in a conventional firearm of the type described each time the trigger motor is changed from one side to the other of the breech casing, the essence of the present invention. comprising a sea-r slide assembly, may be substituted for the conventional sear slide inasmuch as the overall dimensions of said assembly are such that it is readily accommodated in the sear slide guideway of a conventional breech bolt.

Referring to Fi s. 1 through 3, and particularly to Fig. 3, the sear slide assembly comprises a pair of interfitting members 62 and 64 which are independently slidably mounted within the guideway 52. Said members are each reduced in thickness partially of their length to respectively form complemental recesses 66 and B8 in said members. These recesses respectively slidably accommodate the inner end of the other member. Said inner ends of said members are also respectively provided with inclined faces 10 and 12 which function similarly to the inclined face 60 of the conventional sear 54.

Members 62 and B4 are also respectively provided with cam notches I4 and 16 each having a face engageable with one of the opposed cam faces 48 and 50 of the sear projection 46. The inner ends of the members 62 and 64 are reduced in width between the inclined faces HI and I2 and the notches l4 and 76 in order that said inner ends 01' the members may be introduced within the guideway 52 until they reach their 01:- erative position and the projection 46 is disposed within the notches l4 and 16. The purpose of the reduction in width of the inner end of the members 62 and 64 is the same as that with reard to sear slide 54. It will be noted that the longer faces of notches i4 and 18 comprise the active cam faces of said notches and the major portion of each of said active cam faces is not narrowed, whereby no undue wearing of said faces will result, notwithstanding the reduction of the thickness of the inner ends of members 82 and 64 to form recesses 66 and 68.

The outer or larger end of each of members 62 and 84 respectively normally extends within the guideway 52 to a position adjacent the opposite ends of the guideway, whereby said outer ends of said members are substantially flush with the opposed sides of the breech bolt 24.

The members 52 and 64 are respectively slidably guided within the guideway 52 by means of opposed ribs 18 and formed respectively on the upper and lower edges of said members. The ribs 18 and 80 are received within the channels formed in the upper and lower walls of the guideway 52. The upper ribs 18 and 80 of said members are reduced in width for the greater portion of their length but, when the members are mounted in assembled relationship, the juxtaposed portions of said upper ribs which are reduced in width supplement each other to provide properly guided slidable movement for the upper edges of either of said members when moved independently of the other member.

It will thus be seen that the sear slide assembly comprising the essence of the present invention, when mounted in combination with the otherwise conventional cooperating and interconnected parts of the firearm, will serve to actuate the sear to release the firing pin from cocked position, whether the trigger motor is mounted on the right side or the left side of the breech casing and without requiring a reversal of any parts of the sear slide assembly or any dismounting or changing of the parts of the firearm. Thus. should the trigger motor be changed from one side to the other of the breech casing, it will no longer be necessary to service the firearm to the extent of reversing a sear slide as has previously been necessary and is still required with respect to firearms having conventional sear slides of the type illustrated in Fig. 4. Therefore, when said above-described sear slide assembly is substituted for a conventional sear slide, no loss of use of a firearm will be experienced relatively to firearms which are inaccessibly mounted during combat as was previously the situation when a sear slide was inadvertently not reversed in its guideway after the trigger motor had been changed from one side to the other of the breech casing. The sear slide assembly comprising the present invention may be substituted for the conventional single sear slides presently in use in large numbers without modifying either the firearms or trigger motors in any Way.

During the operation of said sear slide assembly, when one of the members 62 or 54 is moved inward to depress the sear and release the firing pin, the other member will be prevented from moving outward of the guideway through the adjacent slot in the side plate inasmuch as the lower edge of the outer end of both of said members is respectively below the lower wall of each of slots l6 or la in said side plates.

Terms used to indicate position, direction and location such as rearward, forward, upper, lower, left hand side, right hand side, and the like are to be considered when the firearm is mounted in its normal position which is that shown in the drawing when the sheet containing the same is held in a vertical position and the left hand end of Fig. 1 is considered the rearward end of the breech bolt and Fig. 2 is considered to be a vertical rear elevation of the firearm. Said terms are to be considered in the same relative sense regardless of the position in which the firearm may be ultimately disposed.

While the invention has been illustrated and described in its preferred embodiment and has included certain details, it should be understood that the invention is not to be limited to the precise details herein illustrated and described since the same may be carried out in other ways,

falling within the scope of the invention as claimed.

What I claim is:

1. An automatic firearm having a breech casing provided with similar means at opposite sides thereof each adapted for the attachment of a trigger motor, a breech bolt within the casing and reciprocable upon recoil from and to firing position, a spring actuated firing pin movable longitudinaliy of the breech bolt and provided with a sear engaging shoulder, a scar reciprocably carried ::;y the breech bolt and provided with a latch engageabie with said shoulder on said firing pin to hold said pin in cocked position and said sear also being provided with a pair of opposed cam faces, said breech bolt also havin a guideway adjacent said scar and extending transversely to the path of movement of said sear, in combination with sear operating mechanism constructed and arranged to permit the same to be slidably mounted in said guideway while said sear remains in operative position in the breech bolt, said mechanism comprising in combination, a pair of members individually guidably mounted in said guideway and respectively extending inward from opposite ends thereof, each member having a cam face engageable with one of the cam faces of said sear for effecting firing pin releasing movement of the sear when either of said members is actuated, and the outer end of each of said members being respectively engageable by a trigger motor to actuate said sear when said motor is mounted on the side of the breech casing adjacent the respective outer end.

2. An automatic firearm having a breech casing provided with similar means at opposite sides thereof each adapted for the attachment of a trigger motor, a breech bolt within the casing and reciprocable upon recoil from and to firing position, a spring actuated firing pin movable longitudinally of the breech bolt and provided with a sear engaging shoulder, a scar reciprocably carried by the breech bolt and provided with a latch engageable with said shoulder on said firing pin to hold said pin in cocked position and said sear also being provided with a pair of opposed cam faces, said breech bolt also having a guideway adjacent said scar and extending transversely to the path of movement of said sear, in combination with sear operating mechanism constructed and arranged to permit the same to be slidably mounted in said guideway while said sear remains in operative position in the breech bolt, said mechanism comprising in combination, a pair of members individually guidably mounted in said guideway and respectively extending inward from opposite ends thereof, each member having a cam face intermediately of its ends engageable with one of the cam faces of said sear for effecting firing pin releasin movement of the sear when either of said members is actuated, the inner ends of said members overlapping within said guideway and the outer end of each of said members being respectively engageable by a trigger motor to actuate said sear when said motor is mounted on the side of the breech casing adjacent the respective outer end.

3. An automatic firearm having a breech casing provided with similar mean at opposite sides thereof each adapted for the attachment of a trigger motor, a breech bolt within the casing and reciprocable upon recoil from and to firing position, a spring actuated firing pin movable longitudinally of the breech bolt and provided with a sear engaging shoulder, a scar reciprocably carried by the breech bolt and provided with a latch engageable with said shoulder on said firing pin to hold said pin in cocked position and said sear also being provided with a pair of opposed cam faces, said breech bolt also having a guideway adjacent said scar and extending transversely to the path of movement of said sear, in combination with sear operating mechanism constructed and arranged to permit the same to be slidably mounted in said guideway while said sear remains in operative position in the breech bolt, said mechanism comprising in combination, a pair of members individually guidably mounted in said guideway and respectively extending inward from opposite ends thereof, each member having a cam face intermediately of its ends engageable with one of the cam faces of said sear for effecting firing pin releasing movement of the sear when either of said members is actuated, the inner ends of said members overlapping and being respectively complementally recessed on their juxtaposed surfaces to accommodate a portion of the other member and the outer end of each of said members being respectively engageable by a trigger motor to actuate said sear when said motor is mounted on the side of the breech casing adjacent the respective outer end 4. An automatic firearm having a breech casing provided with similar means at opposite sides thereof each adapted for the attachment of a trigger motor, a breech bolt within the casing and reciprocable upon recoil from and to firin position, a spring actuated firing pin movable longitudinally of the breech bolt and provided with a sear engaging shoulder, a sear reciprocably carried by the breech bolt and provided with a latch engageable with said shoulder on said firing pin to hold said pin in cocked position and said sear also being provided with a pair of opposed cam faces, said breech bolt also having a guideway adjacent said scar and extending transversely to the path of movement of said sear, in combination with sear operating mechanism constructed and arranged to permit the same to be slidably mounted in said guideway while said sear remains in operative position in the breech bolt, said mechanism comprising in combination, a pair of members individually guidably mounted in said guideway and respectively extending inward from opposite ends thereof, the inner ends of said members overlapping and said overlapping ends being respectively complementally reduced in thickness to provide a recess to accommodate the inner end of the other member, each member also having a cam notch extending inward from one edge of its reduced portion and the Walls of each notch being engageable with a cam face of said sear for effecting firing pin releasing movement of the sear when either of said members is actuated, the outer end of each of said members being respectively engageable by a trigger motor to actuate said sear when said motor i mounted on the side of the breech casing adjacent the respective outer end.

5. An automatic firearm having a breech casing provided with similar means at opposite sides thereof each adapted for the attachment of a trigger motor, a breech bolt within the casing and reciprocable upon recoil from and to firing position, a spring actuated firing pin movable longitudinally of the breech bolt and provided with a sear engaging shoulder, a sear reciprocably carried by the breech bolt and provided with a latch engageable with said shoulder on said firing pin to hold said pin in cocked position and said sear also being provided with a pair of opposed cam faces, said breech bolt also having a guideway adjacent said scar and extendin transversely to the path of movement of said sear, in combination with sear operating mechanism constructed and arranged to permit the same to be slidably mounted in said guideway while said sear remains in operative position in the breech bolt, said mechanism comprising in combination, a pair of members individually gui ably mounted in said guideway and respectively extending inward from opposite ends thereof, the inner ends of said member overlapping and said overlapping ends being respectively complementally reduced in thickness to provide a recess to accommodate the inner end of the other member, each member also having a cam notch extending inward from one edge of its reduced portion and the walls of each notch being engageable with a cam face of said sear for effecting firing pin releasing movement of the sear when either of said members is actuated, the inner end of each of said members being reduced in width between said end and the cam notch to provide a space to clear said cam faces of said i I sear during insertion or removal of said member in or from said guideway and the outer end of one of said members being respectively engageable by a trigger motor to actuate said sear when said motor is mounted on the side of the breech casing adjacent the respective outer end.

6. A sear slide assembly operable from either side of a firearm and constructed for use in a conventional sear slide said assembly comprising in combination, a pair of elongated members constructed and arranged to overlap for a portion of their length and each provided with a complemental recess longer than and accommodating the overlapping portion of the other member, said members each having a guideway in a breech bolt,

10 cam surface formed on the overlapping portion thereof and arranged to be moved independently of each other to coact with and actuate a sear when operatively assembled in the sear slide guideway.

7. A sear slide assembly operable from either side of a firearm and constructed for use in a conventional sear slide guideway in a breech bolt, said assembly comprising in combination, a pair of elongated members constructed and arranged to overlap for a portion of their length and each provided with a complemental recess longer than and accommodating the overlapping portion of the other member, said members each having a cam notch extending inward from one edge of the overlapping portions thereof and said notches normally coinciding and arranged to be moved independently of each other to coact with and actuate a scar when operatively assembled in the sear slide guideway.

8. A sear slide assembly operable from either side of a firearm and constructed for use in a conventional sear slide guideway in a breech bolt, said assembly comprising in combination, a pair of elongated members each formed with longitudinally extending guide means on opposed edges cooperable with means in said guideway and said members being constructed and arranged to overlap longitudinally for a portion of their length and each member also being provided with a complemental recess longer than and accommodating the overlapping portion of the other member, said members each additionally having a cam notch extending inward from one edge of the overlapping portions thereof and said notches normally coinciding and arranged to be moved independently of each other to coact with and actuate a sear.

9. A sear slide assembly operable from either side of a firearm and constructed for use in a conventional sear slide guideway in a breech bolt, said assembly comprising in combination, a pair of elongated members constructed and arranged to overlap longitudinally for a portion of their length and each provided with a complemental recess longer than and accommodating the overlapping portion of the other member, said members each having a cam notch extending inward from one edge of the overlapping portions thereof and said notches normally coinciding and arranged to be moved independently of each other to coact with and actuate a sear when said members are operatively assembled in the sear slide guideway, the overlapping portion of each member also being reduced in width between its notch and overlapping end to facilitate the introduction of each member into coacting relationship with a sear incident to mounting said members in the sear slide guideway.

LAURENCE H. MCCLURE, Jn.

Certificate of Correction LAURENCE H. McCLURE, JR.

It is hereby certified that error appears in the printed specification of the above numbered patent re uiring correction as follows: Column 10, line 38, claim 8, after the word sear an before the period insert when operatz'oely assembled in the sear slide guideway; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the casein the Patent Ofiice.

Signed and sealed this 22nd day of October, A. D. 1946.

Patent No. 2,404,881. July 30, 1946.

LESLIE FRAZER,

First Assistant Oonmz'asimer of Patents. 

